Marine riser assembly

ABSTRACT

A marine riser assembly having a first tubular member having an external surface with a plurality of first axially spaced formations, a second tubular member having an external surface with a plurality of second axially spaced formations thereon, a segmented ring in surrounding relationship to the first and second tubular members, the segmented ring having an inner surface with a plurality of formations engageable with the formations on the first and second tubular members, the engageable formations serving to urge the first and second tubular members toward each other when the segmented ring is subjected to radially inwardly directed compressive forces, a sleeve in surrounding relationship to force the engageable formations together and a seal assembly for sealing against external and internal pressure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to marine riser assemblies.

2. Description of Prior Art

Drilling, production and completion of offshore wells from a floatingplatform, e.g., a vessel, tension leg platform, etc. is typicallyconducted through a riser assembly which extends from the platform tothe wellhead on the sea floor. The riser assembly typically comprises aseries of pipe sections connected end to end. The prior art abounds withnumerous methods to connect the individual pipe sections making up themarine riser assembly and includes threaded connections, weld-onconnectors, etc. While the platform from which the wellbore activitiesare being conducted is maintained as nearly as possible in the fixedposition above the wellhead, there is always some variation in thisrelationship, such that there is relative lateral and vertical shiftingbetween the two. Accordingly, the riser assembly must accommodate thisrelative movement between the platform and the wellhead as well asforces acting on the riser assembly from waves, currents and the like.Since the riser assembly is made up of various individual pipe sections,the connections between the pipe sections are required to withstandwhatever flexing and moving forces occur in the riser assembly and stillmaintain sealing integrity.

SUMMARY OF THE INVENTION

In one preferred aspect, the present invention provides a riser assemblycomprising a first tubular member having a first end face and anexternal surface with a first set of formations thereon. There is asecond tubular member having a second end face and an external surfacewith a second set of formations thereon. A segmented ring is insurrounding relationship to the first and second tubular members, thesegmented ring having an inner surface with a third set of formationsengageable with the first set of formations and a fourth set offormations engageable with the second set of formations. The first andsecond set of formations have engageable surfaces to urge the first endface towards the second end face when the segmented ring is underradially inwardly directed compressive force. The second and fourth setof formations have engageable surfaces to urge the second end facetoward the first end face when the segmented ring is under radiallyinwardly directed compressive force. An annular sleeve is in surroundingrelationship to the segmented ring. The segmented ring and said annularsleeve have inner and outer surfaces, respectively, the engagement ofthe inner and outer surfaces exerting the compressive force. There isalso a seal assembly that seals against external and internal pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational, cross-sectional view of one embodiment of theriser assembly of the present invention.

FIG. 2 is a cross-sectional view taken along the lines 2-2 of FIG. 1.

FIG. 3 is a cross-sectional view taken along the lines 3-3 of FIG. 1.

FIG. 4 is a elevational, cross-sectional view of another embodiment ofthe present invention.

FIG. 5 is a cross-sectional view taken along the lines 5-5 of FIG. 6.

FIG. 6 is a detailed view of the circled section shown in FIG. 6.

FIG. 7 is a elevational, cross-sectional view of another embodiment ofthe present invention.

FIG. 8 is a cross-sectional view taken along the lines 8-8 of FIG. 7.

FIG. 9 is an elevational view, partly in section, showing the embodimentof FIGS. 7 and 8 being assembled.

FIG. 10 is a detailed view of the circled areas shown in FIG. 1.

FIG. 11 is a fragmentary, cross-sectional view of another embodiment ofthe present invention.

FIG. 12 is a fragmentary, elevational, cross-sectional view of anotherembodiment of the present invention.

FIG. 13 is a fragmentary, elevational, cross-sectional view of anotherembodiment of the present invention.

FIG. 14 shows the embodiment of FIG. 13 in an assembled condition.

FIG. 15 is a fragmentary, elevational, cross-sectional view of anotherembodiment of the present invention; and

FIG. 16 shows the embodiment of FIG. 15 in an assembled condition.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the description which follows, like components have been given likereference numerals or characters.

Referring first to FIG. 1, there is shown a riser assembly according tothe present invention indicated generally as 10, the riser assembly 10comprising a first tubular member 12 and a second tubular member 14.First tubular member 12 has an upset portion 16 while second tubularmember 14 has an upset portion 18. Tubular member 12 has a first endface 20 while tubular member 14 has an end face 22. As seen, end faces20 and 22 are adjacent one another and preferably in abuttingrelationship. Tubular member 12 has an annular counterbore 24 whiletubular member 14 has an annular counterbore 26, counterbores 24 and 26being in register and cooperating to form an annular, radially inwardlyopening recess or guide receptacle. First tubular member 12 has anannular, axially extending groove 28 communicating with counterbore 24while second tubular member 14 has an annular axially extending groove30 communicating with counterbore 26. Received in the guide receptacleformed by counterbores 24 and 26, is a guide sub shown generally as 32,guide sub 32 being generally T-shaped when viewed in transversecross-section and having an annular, radially inwardly extending rib 34and first and second annular, axially extending flanges 36 and 38,flange 36 being received in groove 28, flange 38 being received ingroove 30. As shown, flanges 36 and 38 are in engagement with theaxially facing end walls forming grooves 28 and 30. Formed between rib34 and first tubular member 12 is an annular radially inwardly facingrecess 40, a similar annular radially inwardly facing recess 42 beingformed between rib 34 and second tubular member 14. Received in recesses40 and 42 are resilient seal rings, e.g., C rings, 43 and 44,respectively. Radially outwardly from guide sub 32 is an annular recess44 formed by and between end faces 20 and 22. Received in recess 44 is aresilient seal ring, e.g., a C ring 46. As seen in FIG. 10, seal rings43, 44 and 46 are C seals and provide an effective yet non-limiting wayto ensure both contact and pressure energized sealing to seal againstexternal and internal pressures. Although C seals are considered to bestatic seals, they can be pressure energized and are ideally suited forhigh temperatures that conventional elastomeric seals can not withstand.As is well known to those skilled in the art, C seals are generallydesigned for high pressure use. C seals can assume a shape wherein whenthey are compressed or pressure energized the diameter changes. Thisfeature enables a clearance for the seal in the cavity at installationand a tighter fit between seal and cavity upon compression. This occursas the seal outer diameter grows or seal inner diameter shrinks for aninternal pressurized versus externally pressurized seal, respectively.As shown in FIG. 10, the seals 43 and 44 have their mouths open to theinternal pressure inside tubular members 12 and 14 whereas seal 46 hasits mouth open to the external pressure which would be acting upontubular members 12 and 14. Accordingly, when pressure entered the seals43 and 44 they would be forced into tighter engagement with the axialwalls on either side of recesses 40 and 42. Likewise, when pressureentered seal ring 46 the seal would be forced into engagement with theaxially facing walls forming seal cavity 44. C seals can be made from avariety of metallic materials. Typically, the body of such seals is madefrom a relatively rigid material which can be plated or coated with asoft metal plating which when the seal is installed will plasticallydeform into and fill surface imperfections or asperities in the controlsurfaces. For example, the body of the seal can be made from INCONEL orsimilar type materials with a coating of gold, silver or other softermetals which can conform to any irregularities as discussed above.

Formed on upset portion 16 of tubular member 12 are a series ofalternating, annular grooves 48 and annular projections 50. Projections48 have load flanks 52. In a similar manner, formed on the upset portion18 of tubular member 14 are a series of alternating, annular grooves 54and annular projections 56. Projections 56 have load flanks 58. As seen,load flanks 52 face away from end face 20 of tubular member 12 whileload flanks 58 face away from end face 22 of tubular member 14.

Disposed in surrounding relationship to tubular members 12 and 14 is asegmented ring 70. As best seen with reference to FIG. 2, segmented ring70 comprises three individual sections 70A, 70B and 70C. Each ofsections 70A, 70B and 70C are provided on their radially, inwardlyfacing surfaces with a first series of annular projections 72alternating with a first series of annular recesses 74. Each of sections70A, 70B and 70C also is provided with a second set of alternatingannular projections 76 and annular grooves 78. Projections 72 areprovided with load flanks 73 while projections 76 are provided with loadflanks 77.

Annular projections 72 and grooves 74 are generally complementary toannular projections 50 and grooves 48 while annular projections 76 andgrooves 78 are generally complementary to annular projections 56 andannular grooves 54. Stated differently, and as seen, projections 72 arereceivable in grooves 48 while projections 76 are receivable in grooves54. Basically, the interengaged projections and grooves are symmetricabout an imaginary plane passing through and parallel to the abuttingend faces 20 and 22. Basically, and with respect to the imaginary plane,it can be seen that projections and grooves 50 and 48 on tubular member12 are a mirror image of projections and grooves 56 and 54 on tubularmember 14. Likewise, projections and grooves 72 and 74 are mirror imagesof projections and grooves 76 and 78 on segmented ring 70. It needs tobe understood that the respective engaged formations need notnecessarily be the same. For example, the formations on tubular member14 could be different from the formations on tubular member 12. In sucha case, the formations on segmented ring 70 which engage the formationson tubular member 12 would be different from the formations on segmentedring 70 that engage the formations on tubular member 14, the idea beingthat the respective engaged formations be generally complementary to oneanother.

Received over segmented ring 70, is a sleeve shown generally as 82,sleeve 82 having a frustoconical, internal surface 84 which iscomplementary to frustoconical surface 80 formed by the individualsegments 70A, 70B and 70C of segmented ring 70. Although the surfaces 84and 80 are shown as being frustoconical, it will be apparent that othersurface and shapes, including interengaged formations on the surfaces 84and 80 could be employed, provided that sleeve 82 could be axiallyforced over segmented ring 70 and exert a radially inwardly directedcompressive force against segmented ring 70. Segmented ring 70 also hasan annular groove 71 which is in register with an annular groove 85 insleeve 82. Received in the registering grooves 71 and 85 is a snap ring86.

As noted, when sleeve 82 is forced over the external surface ofsegmented ring 70, an inwardly directed compressive force, actually ahoop force, will be exerted on segmented ring 70. Because of the anglesof the grooves and projections on the tubular members 12 and 14 and thesegmented ring 70, the tubular members 12 and 14 will be forced towardone another, i.e., end faces 20 and 22 will be forced towards oneanother. In this regard, it will be appreciated that the force exertedby sleeve 82 will force load flanks 52 and 73 into engagement forcingtubular member 12 towards tubular member 14 while the engagement of loadflanks 58 and 77 will force tubular member 14 towards tubular member 12.In effect, a camming action occurs between the load flanks. Effectively,this will force end faces 20 and 22 into engagement albeit not in fluidtight engagement but, as noted above, fluid sealing against internalpressure will be provided by seal rings 43 and 44 while fluid sealingagainst external pressure will be provided by seal ring 46.

Referring now to FIG. 4, there is shown another embodiment of thepresent invention. The embodiment shown in FIG. 4 differs from thatshown in FIGS. 1-3 primarily in the sealing assembly designed to sealagainst external and internal pressure. The riser assembly, showngenerally as 100, in FIG. 4 comprises a first tubular member 102, asecond tubular member 104, a segmented ring 106 and an external sleeve108. As can be seen, tubular members 102, 104 and segmented ring 106which is comprised of segments 106A, 106B and 106C (see FIG. 5) all havea plurality of alternating, annular projections and grooves which engagesimilarly formed projections and grooves on the exterior surface oftubular members 102 and 104. As in the case of the embodiment shown inFIG. 1, the formations, i.e., the grooves and the projections, areprovided with engageable load flanks as described above with respect tothe embodiment of FIG. 1, such that when the segmented ring 106 is undera radially inwardly directed compressive force, e.g., by sleeve 108, theengaged load flanks segmented ring 106 and tubular member 102 will forcetubular member 102 towards tubular member 104 and likewise the engagedload flanks between segmented ring 106 and tubular member 104 will forcetubular member 104 towards tubular member 102.

Tubular member 102 has a counterbore having an annular, radiallyinwardly facing wall 110 and a generally axially facing chamferedsurface 112. Likewise, tubular member 104 has an annular, radiallyinwardly facing wall 114 and a chamfered surface 116. Walls 112 and 114combined with surfaces 110 and 116 cooperate to form an annular,radially inwardly opening guide receptacle which, as seen, when viewedin transverse cross-section is in the shape of a trapezoid. Received inthe annular trapezoidal shaped guide receptacle is a guide ring 118which, as seen has a shape complementary to the guide receptacle.

A first annular pocket 120 is formed by and between the adjacent endfaces of tubular members 102 and 104. Received in the annular pocket isa C seal 122. There is a second annular pocket 124 formed by and betweenthe adjacent end faces of tubular members 102 and 104, a C seal ring 126being received in pocket 124. As seen, pocket 118 is radially inwardlyfrom pocket 124 and seals against internal pressure in the tubularmembers 102 and 104 while seal ring 126 disposed in the radiallyoutermost pocket 124 seals against external pressure acting upon tubularmembers 102 and 104. An anti-rotation pin 130 is disposed in registeringbores 132 and 134 in the adjacent end faces of tubular members 102 and104, respectively. The encircled area of FIG. 1 is shown in FIG. 6. Ascan be seen, the segmented ring 106 is provided with a series ofannularly extending, axially spaced reliefs 140-148 which decrease inradial depth but which serve to provide the riser assembly with greaterflexibility.

Referring now to FIG. 7, there is shown another embodiment of thepresent invention. There is a first tubular member 200 having an endface 202 and a second tubular member 204 having an end face 206, endfaces 202 and 206 being adjacent one another and preferably inengagement. Similar to the embodiment shown in FIG. 1, tubular members200 and 204 have registering counterbores 208 and 210, respectively.Formed in first tubular member 200 is an annular, axially-facing groove212 which opens into counterbore 208 while an annular, axially facinggroove 214 in tubular member 204 opens into counterbore 210. Annularguide 216, like guide 32 shown in FIG. 1 is generally T-shaped incross-section and has an annular, axially extending flange 218 which isreceived in groove 212 but is spaced from an end wall 220 in groove 212.Likewise, a second annular, axially extending flange 222 is received ingroove 214 but is spaced from an end wall 224 forming groove 214. Therethus are formed seal ring pockets in which are received C seal rings 226and 228, respectively, seal rings 226 and 228 providing sealing againstinternal pressure. To provide sealing against external pressure, the endfaces 202 and 206 cooperate to form an annular recess 230 in which isreceived a C seal ring 232.

The primary difference between the embodiments shown in FIG. 7 and theembodiments shown in FIGS. 1-6 is that the segmented ring 240 ratherthan being formed from a series of individual segments is a monolithicbody. As best seen with reference to FIGS. 7-9, segmented ring 240 hasan annular wall 242, a first end 244 and a second end 246. A series ofcircumferentially spaced, axially extending slits 248 extend from andthrough first end 244 and annular wall 242 to bores 250 distal secondend 246. Likewise, there are a series of circumferentially spacedaxially extending slits 252 which extend from and through first end 246and annular wall 242 to bores 254 distal first end 244. As best seen inFIG. 8, slits 246 and 252 circumferentially alternate around segmentedring 240. The result is that there are formed a series ofinterconnected, axially extending, circumferentially expandable,alternating fingers 260 and 262. As can be seen, segmented ring 240 hasan external, frustoconical surface 270. Received over external surface270 of segmented ring 240 is an annular sleeve 272, annular sleeve 272having an internal surface 274 which is frustoconical and complementaryto surface 270. It will thus be seen, as in the embodiments describedabove, that when sleeve 272 is forced over segmented ring 240, tubularmember 200 will be urged towards tubular member 204 and vice versa dueto interengagement of load flanks, as described above with respect tothe embodiments shown in FIGS. 1 and 4 on the engaged formations oftubular members 200, 204 and segmented ring 240.

In effect, segmented ring 240 is a collet which can be expandedcircumferentially. In this regard, to assemble the riser assembly ofFIG. 7 after guide 216 and seal rings 217 and 219 are in place, tubularmember 200 is forced into ring 240 as shown in FIG. 9. At this point, itcan be seen that the formations, i.e., the alternating projections andgrooves on ring 240 would not be engaged with the projections of tubularmember 204. By now forcing tubular member 204 into segmented ring 240 ina direction towards tubular member 200, the formations on segmented ring240 and tubular member 204 will now be fully engaged as shown in FIG. 7.At this point, outer sleeve 272 can then be forced over segmented ring240 resulting in a camming action by the load flank on the formations onsegmented ring 240 against the load flank on formations of tubularmembers 200 and 204 forcing tubular members 200 and 204 towards oneanother and preferably faces 202 and 206 into engagement.

While the segmented ring 240 or collet has been described as being amonolithic, annular body, it is to be understood that ring 240 could beformed of a plurality of segments which cooperate to form an annularbody. Thus, each section would have first and second ends and a wallwith alternating slits as described above with respect to segmented ring240. Thus, the individual segments could be used in the same manner asdescribed above with respect to the other segmented rings made ofindividual sections. Indeed, in cases where a collet such as segmentedring 240 was employed in the form of segmented sections, the ability tocircumferentially expand the fingers, as described above, would allowgreater flexibility in the sense that each of the individual segmentscould, prior to being engaged with the tubular members, be in asubstantially planar form, i.e., they could be wrapped around thetubular members. Thus, for example, such a collet assembly could be asingle planar piece which was sized such that when it was wrapped aroundthe tubular members, the sides along which the collet was split could beplaced in close contact. Indeed, in certain situations such a form ofthe segmented ring 240 might be easier to install since it could bewrapped around the end of one of the tubular members carrying theformations and the two abutting sides welded together whereupon thesecond tubular member could be forced into the other end of the collet.

In the description above with respect to the segmented ring, thealternating slits are described as extending through the first end inthe wall to bores distal the opposite wall. It will be understood thatwhen the slits are described as terminating distal the first or secondends, e.g., ends 244 and 246, that such termination of the slits will beat a point close enough to the respective end such that the collet hassufficient flexibility to allow the fingers to expand. Indeed it will berecognized that the closer the slits are to be end before which theyterminate, the more flexible the collet will be. Accordingly, thedistance between the inwardly terminating end of the slits and the endof the collet to which those terminating ends are closest will varydepending upon the wall thickness, the degree of flexibility desired,etc. However, for a desired degree of flexibility, knowing the wallthickness, the distance can be readily determined.

The collet or segmented ring 240 can be used in many applications notassociated with the connection of tubular members as described above. Inthis regard, the segmented ring would not have to have the formations asshown and described on the inner surface. For example, such a colletwould be used if it were simply desired to connect two, generallycylindrical bodies together albeit not in a manner that they would be sotightly connected if inter-engaged formations were on the collet and thecylindrical bodies.

Turning to FIG. 11, there is shown another embodiment of the presentinvention. First and second tubular members 300 and 302 have adjacentend faces 304 and 306. End face 304 has an annular, trapezoidal shapedgroove 308 while end face 306 has a registering, annular trapezoidalshaped groove 310. Received in registering grooves 308 and 310 is anannular seal ring 312 which is metallic and which is complementary inshape to the overall groove formed by the combination of grooves 308 and310. Thus, as seen, seal ring 312 has a generally hexagonalconfiguration when viewed in transverse cross-section, i.e., it isessentially formed of two adjoined trapezoidal sections. When engaged,and because of proper sizing, seal ring 312 will form a metal-to-metalseal with grooves 308 and 310 thus effectively acting as a seal againstboth internal and external pressure.

FIG. 12 shows another embodiment for effecting a seal assembly againstexternal and internal pressures. A first tubular member 400 has an endface 402 in which is formed an annularly extending, axially facinggroove 404. Second tubular member 406 has an end face 408 from whichextends an annular projection 410, projection 410 being generallycomplementary in shape to groove 404. Accordingly, when first and secondtubular members 400 and 406 are brought together, and since projection410 and groove 404 are properly sized and in register, projection 410will engage groove 404 in a metal-to-metal sealing arrangement.

Although in the description above, the formations on the tubular membersand on the segmented rings have been described in terms of axiallyspaced alternating, annular grooves and projections, it will be apparentthat the grooves and projections need not be completely annular, i.e.,there could be discontinuities. It is only necessary that the formationson the tubular members and the segmented ring, whatever theirconfiguration, be such that there be surfaces on the segmented ringwhich engage surfaces on the tubular members which, when the segmentedring is subjected to a radially inwardly directed compressive force,force the two tubular members toward one another, preferably inmetal-to-metal relationship.

It will also be appreciated that while the seal rings have beendescribed as being C seals, other seal rings can be employed. Thecharacteristics of the seal rings must be such that they can withstandelevated temperatures and pressures. Thus, although such seals willgenerally be of metallic construction, it is conceivable that certainnon-metallic seals, e.g., certain engineered plastic seals capable ofwithstanding high temperatures and pressures may be employed. Generallyspeaking, however, the seal rings will be metallic in nature. It is alsoto be understood that while a variety of seal assemblies have been shownfor sealing against both internal and external pressure to which thetubular members are subjected, other seal assemblies may be employed.The only requirement of the seal assembly whether it be of the typesshown in FIG. 1, 4, 7, 11, or 12 is that it be capable of creating afluid-tight seal against internal pressure acting from inside thetubular members and external pressure acting externally of the tubularmembers.

It will be appreciated by those skilled in the art that to finallyassemble the riser assembly of the present invention, it is necessary toforce the sleeve over the segmented ring, whether it be the collet shownin FIG. 7 or any of the other segmented rings of the other embodiments.This can be accomplished hydraulically, pneumatically or mechanically.One simple mechanical method of positioning the sleeve over thesegmented ring to achieve a fully assembled marine assembly of thepresent invention is depicted in FIGS. 13 and 14. The embodiment shownin FIGS. 13 and 14 is a modification of the embodiment shown in FIG. 7.Referring then to FIG. 13, tubular member 200A is provided with anexternally threaded, axially extending portion 420, threaded portion 420being near to but extending axially away from formations 240A on collet240. Formations 240A extend from a first end 240B of collet 240. As canalso be seen, the smallest diameter portion 240C on the external surfaceof collet 240 is adjacent first end 240B. In the position shown in FIG.13, it can be seen that end faces 202 and 206 have been brought intoengagement with guide ring 216 and C seals 226, 228 and 232 in place.However, as is also seen the formations, e.g., formations 240A on collet240, have not engaged the formations on the tubular members 204 and200A.

To accomplish this, reference is now made to FIG. 14. Sleeve 272A has afirst end 272B and a second end 272C. Formed on the end 272C is anannular, radially inwardly extending flange 422, flange 422 beingprovided with a threaded portion 424 extending axially therealong,threaded portion 424 being complimentary and threadably mating tothreaded portion 422 on tubular member 200A. As seen, the smallestdiameter portion 274A of surface 274 is proximate flange 422 andaccordingly threaded portion 424.

As sleeve 272A is moved axially in the direction of arrow A, threads 424on flange 422 will come into engagement with threads 420 on tubularmember 200A. Once the threads 420 and 424 have engaged, rotation ofsleeve 272A will force sleeve 272A in the direction of arrow A such thatsurface 274 on sleeve 272A and surface 270 on segmented ring will now beforced into engagement. Rotation of sleeve 272A is continued until thereis essentially full engagement between surfaces 270 and 274, e.g., untilthe formations on collet 240 are in engagement with the formations ontubular members 204 and 200A. At this point, the marine assembly isfully assembled. It should be observed that in FIG. 13 a considerablegap is shown between collet 240 and tubular members 204 and 200A. Thegap has been exaggerated for purposes of showing how the formations oncollet 240 come together with the formations on tubular members 204 and200A under the influence of the force being applied by sleeve 272A as itis threaded axially along tubular member 200A. In point of fact, in thecondition shown in FIG. 13, while the formations would be engaged tosome extent, the engagement would not be sufficient to ensure aconnection with fluid-tight sealing and mechanical integrity.

Referring now to FIGS. 15 and 16 there is shown another mechanicaltechnique for assembling the riser assembly of the present invention.Referring first to FIG. 15, it can be seen that segmented ring 500 has athreaded portion 502 extending axially along the external surface 504 ofsegmented ring 500. Sleeve 506 has an internally threaded, axiallyextending portion 508, the threads of threaded portion 508 mating withthe threads of threaded portion 502. As shown in FIG. 15, sleeve 506 hasbeen moved axially in the direction of arrow B such that there has beenengagement, as shown at 510, between the first thread of threadedportion 508 nearest the end 512 of sleeve 506 and the thread of threadedportion 502 most distal end 513 of segmented ring 500.

Referring now to FIG. 16, it can be seen that continued rotation ofsleeve 506 relative to segmented ring 500 will fully engage the threadedportions 502 and 508 thereby forcing segmented ring 500 radiallyinwardly towards tubular members 200 and 204 which results in forcingthe respective formations in segmented ring 500 into engagement with theformations on tubular members 200 and 204.

While the threaded portion 502 and 508 have been shown as extendingaxially from the ends 513 and 512 of segmented ring 500 and sleeve 506,respectively, it will be appreciated that the threaded portions could beon the opposite ends. Thus threaded portion 508 could be near end 516 ofsleeve 506 while threaded portion 502 could be near end 518 of segmentedring 500. It will also be appreciated that substantially all or in factall of the external surface of segmented ring 500 could be threaded andthat substantially all or all of the internal surface of sleeve 506could be threaded. Lastly, it will be recognized that the threadedportions on segmented ring 500 of sleeve 506 can be positioned anywherealong the axial length of those components, the proviso being that thethreaded portions engage and are threaded together to achieve anassembled condition as shown in FIG. 16. For example, segmented ring 500could have a threaded portion intermediate but distal ends 513 and 518while sleeve 506 could have a segmented portion intermediate but distalends 512 and 516.

The threaded portions used on any of the embodiments shown in FIGS.13-16 can employ any type of thread form as, for example, API threads,buttress threads, etc. It will also be appreciated that for speed ofmake-up, the threaded portions on the segmented ring and the sleeve canbe multi-start, e.g., double-start, four-start, etc.

The terms “near,” “approximate,” or variants thereof, are intended tomean that one surface, component, etc., can engage another surface ofcomponent as well as that one surface, component, etc., can be spacedfrom but in relatively close proximity to a second surface, component,etc.

The embodiments shown in FIGS. 13, 14, 15 and 16 provide an easy methodto not only assemble but also disassemble the marine riser assembly ofthe present invention. Threading of components to assemble anddisassemble them in offshore environments is commonly done and thenecessary equipment is readily available. Thus, while forcing the sleeveover the segmented ring can be done by hydraulic methods, pneumaticmethods, electromechanical methods, etc. The mechanical techniquesdepicted in FIGS. 13, 14, 15 and 16 provide one of the easiest and leastexpensive techniques since it eliminates the need for special hydraulic,pneumatic or electrical power sources. As well, the techniques depictedusing the apparatus as shown in FIGS. 13, 14, 15 and 16 provide an easymethod to disassemble the marine riser assembly since the sleeve can beeasily removed simply by unthreading.

The foregoing description and examples illustrate selected embodimentsof the present invention. In light thereof, variations and modificationswill be suggested to one skilled in the art, all of which are in thespirit and purview of this invention.

1. A marine riser assembly comprising: a first tubular member having a first end face and an external surface, there being a plurality of first, axially spaced, formations on said external surface adjacent said first end face; a second tubular member, said second tubular member having a second end face and an external surface, there being a plurality of second, axially spaced, formations adjacent said second end face, said first and second end faces being adjacent each other; a seal assembly for sealing against external and internal pressure; a segmented ring in surrounding relationship to said first and second tubular members and spanning said adjacent end faces, said segmented ring having an inner surface, there being a plurality of third, axially spaced, formations engageable with said first formations on said inner surface and a plurality of fourth, axially spaced, formations engageable with said second formations on said inner surface, said first and third formation having engaged surfaces urging said first end face toward said second end face when said segmented ring is under radially inwardly directed compressive force, said second and fourth formations having engaged surfaces urging said second end face toward said first end face when said segmented ring is under radially inwardly directed compressive force, said segmented ring having an external surface with at least a portion being tapered, a sleeve having an inner surface with at least a portion having a taper complementary to said tapered portion of said external surface of said segmented ring, said sleeve exerting said compressive force when said tapered surface portions are engaged; an annular guide disposed between said first and second tubular members for maintaining said first and second tubular members generally coaxial, said first tubular member having a first counterbore in said first end face and said second tubular member having a second counterbore in said second end face, said first and second counterbores cooperating to form an annular, radially inwardly extending recess spanning said adiacent end faces, said first tubular member having a first annular, axially extending groove opening into said first counterbore, said second tubular member having a second annular, axially extending groove opening into said second counterbore, said annular guide being generally T-shaped in cross-section and having a first annular, axially extending flange received in said first groove and a second annular, axially extending flange received in said second groove, said first groove having a first annularly extending axially facing end wall and said second groove having a second annularly extending, axially facing end wall, said first flange being spaced from said first end wall, said second flange being spaced from said second end wall thereby forming first and second annularly extending seal ring pockets, respectively; and a first resilient seal ring being received in said first seal ring pocket and a second resilient seal ring being received in said second seal ring pocket.
 2. The riser assembly of claim 1, wherein said first and second seal rings comprise C seals.
 3. The riser assembly of claim 1, wherein there is an annular recess formed by and between said first and second adjacent end faces and there is a resilient seal ring received in said annular recess.
 4. The riser assembly of claim 3, wherein said resilient seal comprises a C seal.
 5. The riser assembly of claim 1, wherein said T-shaped guide includes a radially inwardly projecting, annularly extending rib, said rib having a first axially facing surface and a second axially facing surface, said first flange being in engagement with said first axially facing wall, said second flange being in engagement with said second axially facing wall, a first annular, radially inwardly opening recess formed between said first axially facing surface and said first tubular member and a second annular, radially inwardly opening recess formed between said second axially facing surface and said first tubular member, a first resilient seal ring being received in said first recess, a second resilient seal ring being received in said second recess.
 6. The riser assembly of claim 5, wherein said first and second seal rings are C seals.
 7. The riser assembly of claim 5, wherein there is an annular recess formed by and between said first and second adjacent end faces and radially outwardly of said guide and there is a resilient seal ring received in said annular recess.
 8. The riser assembly of claim 7, wherein said resilient seal comprises a C seal.
 9. The riser assembly of claim 1, wherein said segmented ring comprises an annular body, said annular body having an annular wall, a first end and a second end, a plurality of first, circumferentially spaced slits extending through said first end and said annular wall to a point distal said second end and a plurality of second, circumferentially spaced slits extending through said second end and said annular wall to a point distal said first end, said first and second slits alternating to form a series of interconnected axially extending, circumferentially expandable fingers.
 10. The riser assembly of claim 9, wherein said annular body comprises a plurality of sections.
 11. The riser assembly of claim 9, wherein said annular body is monolithic.
 12. The riser assembly of claim 9, wherein said annular body has a single split extending through the length of the annular body and said first and second ends.
 13. A marine riser assembly comprising: a first tubular member having a first end face and an external surface, there being a plurality of first, axially spaced, formations on said external surface adjacent said first end face; a second tubular member, said second tubular member having a second end face and an external surface, there being a plurality of second, axially spaced, formations adjacent said second end face, said first and second end faces being adjacent each other; a seal assembly for sealing against external and internal pressure; a segmented ring in surrounding relationship to said first and second tubular members and spanning said adjacent end faces, said segmented ring having an inner surface, there being a plurality of third, axially spaced, formations engageable with said first formations on said inner surface and a plurality of fourth, axially spaced, formations engageable with said second formations on said inner surface, said first and third formation having engaged surfaces urging said first end face toward said second end face when said segmented ring is under radially inwardly directed compressive force, said second and fourth formations having engaged surfaces urging said second end face toward said first end face when said segmented ring is under radially inwardly directed compressive force, said segmented ring having an external surface with at least a portion being tapered, said segmented ring comprises an annular body, said annular body having an annular wall, a first end and a second end, a plurality of first, circumferentially spaced slits extending through said first end and said annular wall to a point distal said second end and a plurality of second, circumferentially spaced slits extending through said second end and said annular wall to a point distal said first end, said first and second slits alternating to form a series of interconnected axially extending, circumferentially expandable fingers; and a sleeve having an inner surface with at least a portion having a taper complementary to said tapered portion of said external surface of said segmented ring, said sleeve exerting said compressive force when said tapered surface portions are engaged.
 14. The main line assembly of claim 13, wherein said annular body is monolithic.
 15. The annular body of claim 14, wherein said annular body has a single split extending through the length of the annular body and said first and second ends.
 16. The riser assembly of claim 13, wherein said annular body comprises a plurality of sections. 